Non-aqueous electrolytic solution

Abstract

There is provided a non-aqueous electrolytic solution comprising an electrolyte salt, a specific fluorine-containing solvent and a fluorine-containing cyclic carbonate represented by the formula (A1): wherein X 1 to X 4 are the same or different and each is —H, —F, —CF 3 , —CHF 2 , —CH 2 F, —CF 2 CF 3 , —CH 2 CF 3 or —CH 2 OCH 2 CF 2 CF 3 ; at least one of X 1 to X 4 is —F, —CF 3 , —CF 2 CF 3 , —CH 2 CF 3 or —CH 2 OCH 2 CF 2 CF 3 , and the non-aqueous electrolytic solution has further excellent noncombustibility and is suitable for lithium secondary batteries.

The invention claimed is: 
     
       1. A non-aqueous electrolytic solution comprising:
 (I) a solvent for dissolving an electrolyte salt comprising (A) a fluorine-containing cyclic carbonate represented by the formula (A1): 
 
       
         
           
           
               
               
           
         
         wherein X 1  is —CF 3 —CH 2 CF 3  or —CH 2 OCH 2 CF 2 CF 3 ; and X 2 , X 3  and X 4  each is —H, and 
         (B3) a fluorine-containing chain carbonate, and 
         (C) at least one fluorine-containing solvent selected from the group consisting of (C1) a fluorine-containing lactone, (C2) at least one fluorine-containing solvent selected from the group consisting of monofluorobenzene, hexafluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene and pentafluorobenzene and (C3) a fluorine-containing sulfolane derivative, and 
         (II) an electrolyte salt, and 
         wherein the solvent (I) for dissolving an electrolyte salt comprises 10 to 60% by volume of the fluorine-containing cyclic carbonate (A), 40 to 90% by volume of the fluorine-containing chain carbonate (B3) and 0.5 to 20% by volume of fluorine-containing solvent (C), based on the whole solvent (I). 
       
     
     
       2. The non-aqueous electrolytic solution of  claim 1 , wherein the fluorine-containing solvent (B3) is a fluorine-containing chain carbonate (B3) represented by the formula (B3):
   R 5 OCOOR 6    
 
       wherein R 5  and R 6  are the same or different, each is an alkyl group or fluorine-containing alkyl group having 1 to 4 carbon atoms, at least either R 5  or R 6  is a fluorine-containing alkyl group. 
     
     
       3. The non-aqueous electrolytic solution of  claim 1 , wherein the electrolyte salt (II) is at least one selected from the group consisting of LiPF 6 , LiN(SO 2 CF 3 ) 2  and LiN(SO 2 CF 2 CF 3 ) 2 . 
     
     
       4. The non-aqueous electrolytic solution of  claim 1 , wherein the non-aqueous electrolytic solution is for lithium secondary batteries. 
     
     
       5. The non-aqueous electrolytic solution of  claim 1 , wherein the non-aqueous electrolytic solution is for large size lithium secondary batteries used for hybrid cars and distributed power source. 
     
     
       6. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator and the non-aqueous electrolytic solution of  claim 1 , wherein an active material used on the positive electrode is at least one lithium compound oxide selected from the group consisting of lithium cobalt compound oxides, lithium nickel compound oxides, lithium manganese compound oxides, iron compound oxides and lithium vanadium compound oxides.